In an effort to reduce interference in wireless systems, several beam architectures have been devised and implemented in the wireless communication field. Adaptive antenna implementations use a separate narrow tracking beam for each mobile in order to reduce the amounts of interference transmitted on the forward link and to reduce the amount of interference seen on the uplink. Each user is tracked by a separate beam within a sector. Adaptive antenna systems are generally expensive due to the need for calibration of the signal paths between the baseband processor and the array as well as the need for advanced signal processing.
Switched beam methods are simpler to use than fully adaptive methods. In switched beam implementations, a set of beams is used to cover a sector, satisfying the requirement that all locations in the sector are covered by at least one beam. Calibration is not required for switched beam architectures, if one cable is used per beam. In order to maximize the capacity and coverage increase associated with a fixed number of beams, the beams should exactly cover the area of the sector with minimal overlap between adjacent beams consistent with full coverage of the sector. In the area of overlap, the beams can interfere destructively due to their uncontrolled phase relationship, resulting in nulls or “holes” in the sector coverage in which it is difficult to communicate with a user without greatly increasing the amount of power used to transmit the signal to this user.
This invention presents a method to minimize the creation of nulls within the area of overlapping beams, while simultaneously providing diversity, thus providing a wireless system with increased capacity and coverage.